Field of the Invention
The present invention relates to a liquid crystal composition, and particularly to a liquid crystal composition having large optical and dielectric anisotropies, high clearing point, fast response speed, high resistivity, good high-temperature and UV stability, and to a liquid crystal display (LCD) comprising the liquid crystal composition.
Description of Related Art
The liquid crystal material is a mixture of organic rod-like small molecule compounds having both fluidity and anisotropic properties of liquid crystals at a certain temperature. Liquid crystal materials are primarily used as dielectrics in displays because the optical properties of such materials can be varied by the applied voltage. Liquid crystal displays (LCDs) are displays making use of photoelectric changes, and have become the most popular flat panel displays in recent years, because of their small size, light weight, low power consumption, excellent display quality, and other attractive advantages. The electro-optical modes employed in existing LCD displays include, for example, twisted nematic (TN) mode, supertwisted nematic (STN) mode, optical compensated bend (OCB) mode, electronically controlled birefringence (ECB) mode, and variations thereof. In all of these modes, an electric field that is substantially perpendicular to the substrate or perpendicular to the liquid crystal layer is used. In addition to these modes, there is also an electro-optical mode employing an electric field that is substantially parallel to the substrate or the liquid crystal layer, such as, in-plane switching (IPS) mode.
For such displays, new liquid crystal media with improved performance are desired. Particularly, for many types of application, a liquid crystal medium comprising a liquid crystal composition needs to have a nematic phase over a suitable wide range of temperature, an appropriate birefringence, and a dielectric anisotropy that is high enough to allow a reasonably low operating voltage. Materials for liquid crystal display further need to have a nematic phase over a suitable wide range of temperature, high-temperature stability, and other properties, to meet the requirement for good display effect in various environments.
The liquid crystal compositions suitable for use in LCD and particularly TFT displays are known, for example, from JP07-181439, EP0667555, EP0673986, DE19509410, DE19528106, DE19528107, WO9623851 and WO9628521. However, these liquid crystal compositions suffer from notorious disadvantages. They mostly cause an adversely long response time, have a low resistivity, and need an excessively high operating voltage, among others.
Therefore, in the field of liquid crystal materials, there is particularly a need for a liquid crystal composition having properties needed in practical use, for example, high upper temperature of a nematic phase, appropriate optical anisotropy, good dielectric anisotropy, high-temperature stability, and high resistivity.